HARMONI+Adaptive Optics: a trailblazing combination!

HARMONI, the first-light spectrograph for the Extremely Large Telescope (ELT) has passed a major milestone today in successfully completing the Preliminary Design Review process (PDR). We chatted to HARMONI's Principal Investigator Professor Niranjan Thatte who is leading the international consortium building this sophisticated instrument and what this critical step means for future observations with the ELT.

Perched over 3,000 metres above sea level on top of Cerro Armazones in the Atacama Desert of northern Chile, the ELT will be the biggest telescope ever built working in the visible and infrared wavelength range. It will have a giant main mirror 39 metres in diameter, just shy of two tennis court lengths, being built by the European Southern Observatory (ESO) in one of the biggest global science collaborations in history.

The concept that is now realised as HARMONI, evolved over more than a decade of development since the initial ideas discussed by Oxford astrophysicists Prof Thatte, Matthias Tecza and Fraser Clarke who are now the HARMONI Instrument Scientist and Lead Systems Engineer, respectively. HARMONI is an integral field spectrograph over the visible and near-infrared wavelength ranges. This means that for every pixel in an image HARMONI takes, the light is split up into 4000 individual wavelengths or colours. Such data reveals key information about astronomical objects such as their chemical composition and the way they are moving, that provides clues to their formation and nature. 'HARMONI is a “work-horse” instrument: it will carry out observations of a wide variety of astronomical objects, ranging from planets around nearby stars, to the very first galaxies, and the very first stars ever formed,' Prof Thatte explains.

The HARMONI project is an international collaboration of several universities, institutes and national laboratories, located in the UK, France and Spain. The project is jointly led by the University of Oxford (Principal Investigator: Niranjan Thatte) and the UK Astronomy Technology Centre (Project Manager: Ian Bryson). The PDR assessed the design of the instrument's optics, mechanics, software, and electronics, as well as its operational concepts for which the HARMONI team generated 144 documents answering over 1500 questions! As the first ELT instrument to successfully pass through this phase of review, this is a significant achievement.

In addition, at their December 2018 meeting, the ESO Council (ESO's governing body) approved the design and construction of the Laser Tomographic Adaptive Optics (LTAO) module for HARMONI. LTAO will allow HARMONI to correct for the turbulence of the Earth’s atmosphere, enabling HARMONI to take the sharpest images the telescope can deliver, over the whole sky, thanks to six artificial (laser) guide stars. Prof Thatte says "The images will be over 5 times sharper than the best ground based telescopes can achieve today, and even 10 times sharper than those made using the Hubble Space Telescope. The combination of exquisite detail (from LTAO correction), and extreme sensitivity (from the large light gathering power) will mean that the ELT will stand head and shoulders above any other facility built to date; the full ELT facility will herald a great leap forward in our understanding of the cosmos."

Just as the ELT is extremely large, so is HARMONI. As instruments go, it's one of the largest conceived to date. HARMONI will stand an impressive 8 metres tall, measure 10 metres long by 6 metres wide, and weigh in at a mighty 39 tonnes! This sophisticated instrument is set to revolutionise our understanding of the Universe in the next decade.

We warmly congratulate the entire HARMONI team on their success and look forward to the exciting discoveries HARMONI will make.